Profile rails of the initially named kind are used, for example, in the assembly of grid ceilings. For the assembly of grid ceilings, first, a plurality of profile rails are suspended from the ceiling one after the other in the longitudinal direction and at right angles thereto such that a frame construction is provided which has mutually adjoining rectangular regions into which ceiling panels can be inserted. The panels are first obliquely introduced into the regions between the mutually spaced apart section rails and are subsequently placed onto the inner sides of the bottom chords of the T section rails. The panels are usually additionally secured against lifting upwardly.
The frame construction consists of main T section rails which extend in parallel and between which transverse T section rails are arranged which extend perpendicular to the main T section rails. The main sections and the transverse sections usually have identical structures in this process.
Known profile rails are produced, for example, from a strip of sheet metal which is first folded over by 180° along its central longitudinal axis to form the web such that both halves of the strip of sheet metal each contact one another areally. The two free ends of the bent over strip of sheet metal are each again outwardly folded over by 90° such that they form the two bottom chord sections of the bottom chord of the T section rail produced in this manner.
A top chord, which can be formed, for example, as a hollow section, is usually provided at the longitudinal edge of the profile opposite the bottom chord. A coupling of fastening elements, via which the profile rails can be suspended from the ceiling, is possible via this top chord.
A screening strip is usually provided at the bottom side of the bottom chord by which a clean visual downward termination of the profile rail is achieved.
It is problematic with the profile rails of this type that the web is made with double walls, i.e. with double the material thickness, due to the symmetrical design, which is disadvantageous with respect to the required material effort. Since the required material has a substantial portion of the production costs with profile rails, a reduction of the required material effort is desirable.
Furthermore, openings in the web are usually provided at regular intervals in the profile rails of the initially named kind and form a type of desired kink points for the case of fire. Since the profile rails expand by a relatively large amount due to the high heat development in case of fire, the ceiling suspensions would tear relatively quickly due to these longitudinal expansions without appropriate precautions so that there is a risk that the whole ceiling construction would crash down in case of fire.
Desired kink points are provided by the openings such that, on large expansions due to high heat development, the profile rails kink at the desired kink points due to the forces occurring on the expansion, whereby a tearing of the suspensions is prevented.
If the provided top chord is made as a hollow section, corresponding crimps of the hollow section are usually provided here to produce the required desired kink points.
The production of the desired kink points in the form of additional openings or crimps is associated with additional costs.